A report, being considered by Northumberland County Council's audit committee today, said that an investigation had uncovered "inappropriate" conduct at the authority in relation to the handling of an application for the Dissington Garden Village scheme on the edge of Ponteland.
The development had initially attracted the support of the council, but this changed after a new administration took control in 2017.
Developer Lugano began legal action against the council in September 2018, alleging misconduct at the authority. The council denied the allegations.
Lugano later dropped the legal action, and Northumberland County Council announced that it would seek damages against the developer.
The planning application for the garden village was formally withdrawn in January 2019.
According to the committee report, Northumberland County Council appointed independent investigators after a "whistleblowing" complaint about alleged unethical practices relating to the application.
The report, by chief executive Daljit Lally, said that the investigation had revealed that "conduct in relation to that planning application [was] not transparent or appropriate".
It added: "It appears that significant efforts were made by several persons in positions of authority and control within the county council to collude with and secure a number of inappropriate advantages for the planning applicant/developer in the application in question.
"Such advantages would not be conferred on any other planning applicant in the normal conduct of the authority’s planning functions."
The report said that planning officers recommended approval for the application, even though subsequent advice from the Planning Officers Society, which represents public sector planners, indicated "almost certainly" that "any reasonable planning authority would have recommended the planning application in question for refusal".
The report said that the investigation found evidence that a senior planning officer accepted "substantial hospitality" from the applicant, including first class rail travel, hotel accommodation and a meal in a London restaurant owned by a Michelin-starred chef.
The report said the level of hospitality was "excessive" and that the planning officer had not declared it, contrary to council procedures.
"There is consequently doubt on the behaviour and impartiality of this very senior planning officer, who was in a significant position of authority and control, regarding the planning application in question," the report said.
In addition, the report said that the investigation found evidence of discussions between previous senior management at the council and the developer, including discussions held through a chief officer’s personal email account.
"It is now clear that senior officers within the planning department were similarly using personal email accounts to transact county council business in respect of this same planning application," the report said.
A senior planning officer instructed staff to carry out correspondence relating to the application via personal accounts, "in order that the correspondence would be hidden and not be able to be subjected to potential scrutiny through the expected routes such as audit or Freedom of Information processes", the report said.
In addition, the correspondence "demonstrates a colloquial and inappropriate familiarity between senior planning officers and the planning applicant in question", including gossip relating to another planning application, the report found.
The investigation also found evidence that the applicant and/or their advisers "were invited/allowed by a very senior officer in the planning department to write and alter parts of the planning officers’ report to the strategic planning committee".
The applicant was also allowed to view confidential drafts of the report, Lally’s report said.
"There is therefore serious concern of undue influence/conflict of interest on the part of the planning applicant," the report added.
In addition, the report said that evidence was unearthed that county council officers sought to obtain legal advice to support the planning applicant’s stance, ignore objections and advice by other officers and to overturn decisions made within the wider planning team "without any fair or reasonable rationale".
Lally’s report said that "the conduct of a number of senior officers previously employed by the county council has fallen short of expected standards of behaviour, conduct and ethics and as a result significant concerns have been raised with Northumbria Police and an external referral has been made to the relevant professional body, given the nature of the concerns which have arisen".
However, Northumbria Police have reportedly said that they could not find anything in the information provided by the council last year to warrant a criminal investigation.
The Royal Town Planning Institute was asked by Planning if such a referral had been made but it did not respond.
A Northumberland County Council spokesperson said: "We have a statutory obligation to uphold the duties required as a planning authority.
"It is only right and proper that when significant matters of concern are brought to our attention, that we investigate these fully, and report and act on the findings. These related specifically to the professional conduct and inappropriate behaviour surrounding a significant planning application, which was subsequently withdrawn.
"To confirm, the employees referred to in this report are no longer employed by the council"
Planning contacted Lugano for additional comment but it had yet to respond by the time of publication.